This invention relates generally to granular material spreaders and, more particularly, to a drop spreader apparatus equipped with interchangeable, pre-calibrated distribution gauges.
Granular material spreaders are used in a wide variety of applications, but are used most commonly for the distribution of fertilizers, insecticides, top soil or sand in top dressing applications, as well as for distribution of ice control materials on walkways around buildings and landscaping. Such spreaders may be generally classified in two types, drop spreaders and broadcast or spinner spreaders.
Drop spreaders are well known in the art with several types being described in U.S. Pat. No. 1,256,854, 2,627,364, 2,940,640, and 3,096,004. Typically, drop spreaders include a hopper having a plurality of discharge openings or apertures formed in the bottom through which the granular material is discharged under the action of gravity. In addition, many drop spreaders have a slide plate which can be adjusted for selectively obscuring the discharge openings in the hopper, thereby restricting or interrupting the amount of granular material discharged. Furthermore, some drop spreaders also incorporate an agitator or other device for mechanically disturbing the granular material located above the discharge openings, thereby improving the material flow of material through the openings.
In contrast to drop spreaders, broadcast or spinner type spreaders include a rotating member for centrifugally dispersing or "casting" the material out away from the spreader. The amount and concentration of material disbursed is controlled by metering the amount of material delivered to the rotating member and/or adjusting the speed of the rotating member. Unfortunately, conventional spreaders have not proven to be accurate in delivering a precise amount of granular material over a particular area. Therefore, such spreaders are not generally useful in applications where space is limited and accuracy is important, such as in the distribution of turf control products or ice control materials in close proximity to buildings and landscaping. More particularly, dispersion of ice control materials on lawns and landscaping results in not only a waste of material, but there are also ecological concerns since some ice control materials are harmful to lawns and shrubbery. Alternatively, the dispersion of turf control products onto walkways and driveways is undesirable in that it may eventually be washed into ground water supplies, lakes and streams.
While drop spreaders are more accurate than broadcast spreaders in delivering granular material over a particular area, proper adjustment of the slide plate arrangement associated therewith may prove to be problematic. For example, in dispensing ice control materials it is often desirable to use rock salt and calcium chloride. Rock salt is preferred on thick ice to improve traction and break the ice up so that it may subsequently be removed. Alternatively, calcium chloride is the preferred material when there is light icing since it melts the ice at lower temperatures. In a typical application, rock salt us initially applied to break up the thick ice, followed by application of calcium chloride to prevent the reformation of ice. Unfortunately, to switch between these differing materials with a traditional drop spreader requires significant adjustment to get the proper distribution. Such an arrangement is highly inefficient in that, prior to making the adjustment, either too much or not enough material is spread. Thus, material is either wasted or multiple applications are required.
Another drawback associated with both drop and broadcast spreaders is that the agitator or rotating member is generally connected to or integral with the axle onto which the wheels are mounted. In this arrangement, the tractive engagement between the wheels and the surface over which the material is to be applied causes rotation of the wheel and the axle, thus driving the agitator or rotating member as the spreader is moved about. As can be appreciated, this arrangement is rather ineffective when the surface over which the material is applied is ice covered, since traction is relatively poor.